1. Field of the Invention
The present invention relates to a method of manufacturing a porous ceramic body and a composition for a porous ceramic body, and more particularly, to a method of manufacturing a porous ceramic body and a composition for a porous ceramic body, wherein a coarse particles that is difficult to manufacture in bulk form using pressing, plastic forming or casting as a ceramic forming process is used together with wax, thereby producing a porous ceramic body having good mechanical and leaching properties while retaining excellent dimensional stability and shape stability.
2. Description of the Related Art
A porous ceramic body is used as a material for a filter for separation and recovery of gas, liquid and solid or a filtering support, and a core or a shell mold for forming a specific shape or a channel for metal investment casting.
Typically, a ceramic product is known to undergo a conventional forming process including pressing such as uniaxial or isostatic pressing using metal dies, plastic deformation forming such as extrusion or injection using plasticity, and casting such as slip, tape or gel casting using slurry fluidity. A conventional method of forming a ceramic product employs processing additives that facilitates the formability and working of dispersed fine particles. the example of processing additive are an organic or inorganic binder, a plasticizer, a dispersant, a defoaming agent, water and or an organic solvent. When water or an organic solvent is used as the forming aid in such a way, an additional removal process thereof has to be carried out. In the presence of such an additive system, the ceramic product may easily shrink or distort from the desired shape during heat treatment. Furthermore, the impurities remaining after removal of the solvent deteriorate mechanical properties of the ceramic product. Hence, taking into consideration the eco-friendly and technological benefits of a ceramic manufacturing process, a novel forming method is required, which does not need an additive such as solvent or an organic or inorganic binder.
Powder processing for ceramics generally includes preparing a powder, mixing various powders (or making a slurry), forming a green body in a desired shape and carrying out subsequent heat treatment (drying and sintering) to obtain a dense product for each purpose. As such, the particle size has a direct influence on formability or density of a green and a sintered body. Nano-sized powders that is too small is not easily pressed due to the high surface area relative to the volume, and large powders having a size ranging from ones of mm to hundreds of μm has poor formability due to a remarkably decreased surface area effect. In particular, a fused silica having a size of hundreds of μm is similar to sand and is difficult to be compacted even under high pressure, but a small amount of water or adhesive liquid added into large powders may play a role as a binder to form a predetermined shape. Moreover, a ceramic powder, which is difficult to be compacted alone, may be prepared in the dispersed phase in the dispersing medium (slurry) with the use of an additive such as proper solvent and a dispersant. However, since a ceramic powder having a size of hundreds of μm is larger than a colloid, it is affected by gravity rather than interparticle forces and thus may rapidly settle down, making it difficult to perform colloid processing.
As for powder processing as above, inhomogeneity of the ceramic compacts may be caused from the powder itself and powder (or slurry) preparation, or compaction and densification step. Furthermore, the forming aids including organic additives are primary heterogeneous components in powders. Each heterogeneous component is stress concentrator, which in early stage it makes cracking leading to mechanical failure.